Hydraulic actuators typically use external mechanisms to control the relative positioning of the actuator piston and cylinder. These external mechanisms are erratic in operation and often unreliable. While it is desirable to use hydraulic controls because they are smoother in operation, they have the disadvantage of requiring bulky and heavy flow control valves, shut-off valves, etc. Hydraulic controls are generally not feasible in applications where it is desirable to restrict the weight and size of the actuator components.
As an example, reclining seat backs are popular features on patio and deck furniture, such as chaises longues. When using a chaise longue, a user will have his outstretched legs supported by an elongate seat portion and his back supported by the reclining seat back. The typical range of motion of a reclining seat back is between a substantially vertical or upright position and a fully reclined or horizontal position.
In the past, the operation and control of these reclining seat backs has been effected by the user. Typically, the user must provide the force to raise and lower the seat back as the user is reclining on the seat. In addition, the user must set a latching mechanism at one of several preset locations to hold the seat back in a desired position. Although this type of reclining seat back has been suitable for its purposes, it has several disadvantages.
First, the force required for a user to raise and lower the seat back without assistance may be too great when the user is reclining on the seat, especially for the elderly, young children, and the physically impaired. As a result, the user will either require assistance in raising or lowering the seat back or be forced to stand up to move the seat back to the desired position. Second, the latch mechanisms can be difficult to set and release, especially when incorporated into the arm of a chaise longue, because the user must use the arm for support when moving the seat back into the desired position. Finally, these latching mechanisms are limited in the number of preset seat back positions and do not permit adjustment to any desired angle or degree of inclination.
Although mechanized reclining seat backs have been used in automobiles and household furniture, they are not adaptable to patio furniture because of their size, weight, and the need for electric or hydraulic power. Thus, there is a need for a hydraulic actuation and control system that uses an internal hydraulic control valve that can be easily operated with a remotely positioned control device.